Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare the full safety profile (readOnlyHint, idempotentHint, destructiveHint=false, closed world), so the description carries a reduced burden. It adds the cost tier (50 credits, Tier 3), which is real operational context not present in annotations, but says nothing about what the calculation destroys, requires, or how heavy the response is. Adequate but thin.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded definition followed by a compact metadata block; every line is short and scannable. The [Required: input1, input2] line mildly duplicates the schema's required array, which is the only wasted element in an otherwise tight description.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so return values need not be explained, and the two-chart input is implied by 'between two charts'. Combined with exhaustive per-parameter schema docs and annotations covering the safety profile, nothing an agent needs to invoke this correctly is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, with input1/input2 carrying very detailed nested docs (timezone handling, houseSystem letters, rejected short forms) and precision/fields documented inline. The description only restates the two required parameters, adding nothing beyond what the schema already provides. Baseline 3 applies when the schema does all the heavy lifting.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (calculate) and resource (coalescent chart), and adds a definitional gloss — 'the harmonic chart that resonates most strongly between two charts' — which is genuinely useful for an obscure technique. However, it never distinguishes itself from close siblings like astroway_relational_composite, astroway_relational_davison, or astroway_relational_synastry, so the agent cannot tell from the text alone which two-chart tool to pick.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description gives no when-to-use or when-not-to-use guidance and names no alternatives among the many relational tools. The [Group: Comparisons] tag and [Required: input1, input2] block are structural metadata rather than selection guidance, and the cost line tells the agent the price but not the condition that should make it choose this over a composite or synastry chart.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.